Furnace



Patented May 1:3, 194i.

UNETE FURNACE seits Applica ien February i7, 1938, Serial No. 190,997

3 Claims.

This invention relates to furnaces, and more particularly to an improved construction of furnace in which fuels may be burned either in suspension or in solid form on a grate.

Many manufacturing concerns utilize a fuel such as pulverized coal for a considerable part of their steam generating requirements and supplement this fuel with waste material, as for example wood refuse, resulting from manufacturing operations. Pulverized coal is burned in suspension, Whereas wood refuse is usually burned on -a grate. Because of the great differences in these fuels and in the type of combustion chamber best suited to them, it is a common practice to utilize separate furnaces, but this is expensive, ineicient and wasteful of space.

Itis accordingly one object of the present invention to overcome these difficulties and to provide a comparatively simple and inexpensive steam generating furnace in wh-ich ztwo widely differing fuels may be burned simultaneously or independently.

It is-a further object of the invention to provide a furnace which will occupy comparatively little floor space, and which is adapted for the efficient combustion of one fuel in suspension and of a dierent fuel on a grate.

It is a further object of this invention to provide a furnace adapted for the efficient combustion of pulverized fuel in suspension and of a different fuel in solid form on a grate, the various parts being so constructed and arranged as to ensure automatic discharge of the incombustible residues from both fuels.

With these and other objects in view, as will be apparent .to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

In accordance with our invention in its preg ferred form, we provide a combustion chamber in which a fuel such as pulverized coal may be burned in. suspension, this chamber having two opposite bottom walls which slope downwardly and inwardly toward a narrow central throat or opening extending transversely of the combustion chamber. Beneath this opening there is provided a longitudinally movable grate, which is preferably of the endless type. A solid fuel, such as wood refuse, is supplied to the front of the grate, and the ashes from both fuels `are carried rearwardly by the grate and deposited in a suitable ash pit or sluice. Arches of refractory material extend forwardly and rearwardly from the central opening to ensure-thek ignition and emcient combustion of the solid fuel. These arches are preferably supported by means of water tubes which continue upwardly to form cooling means for the sloping bottom walls of the upper combustion chamber and thus facilitate the discharge by gravity of the pulverized fuel ash.

Referring to the drawing illustrating one ernbodiment of the invention, and in which like reference numerals indicate like parts,

Fig. 1 is a longitudinal sectional View through a steam generating furnace;

Fig. 2 is an enlarged fragmentary section taken on the line 2-2 of Fig. l; and

Fig. 311s an enlarged fragmentary section taken on the line 3-3 vof Fig. 1.

The embodiment illustrated comprises a steam boiler having a transverse lower drum It at the front and a transverse upper drum I I at the rear, thesedrums being connected by a bank of upwardly and rearwardly inclined water tubes I2. Beneath the water tubes I2 there is provided a combustion chamber lli having a front wall I5 and a rear wall I6. The front wall l5 is formed with an opening I3 through which a stream of:

pulverized fuel and combustion air may enter the chamber I4 from a burner I9 of any suitable type. Pulverized fuel is supplied to the burner from a suitable pulverzer 2) through a pipe 2|. The combustion chamber Ill is provided with front and rear bottomvwalls 23 and 2i respectively which slope downwardly and inwardly toward a narrow central ash discharge throator opening 25 extending transversely of the combustion chamber. v

Beneath the ash discharge opening 25 there is provided a longitudinally movable endless grate 2l of any suitable construction, having a fuel hopper 28 at the front thereof toreceive Wood refuse or other fuel by gravity from a feeder 29 through a chute Sli. The upper run of the grate 2l is arranged to travel rearwardly towarda rear wall 32 which is spaced slightly from the rear end of the grate to provide room for the downward discharge of ashes.

In order to protect the grate 2l from the radiant heat of .the combustion chamber Ill and at the same time facilitate the ignition and com bustion of the fuel on the grate, we provide a substantially horizontal front arch il@ spaced above the grate and extending forwardly from the transverse opening 25, and a substantially horizontal rear arch t5 spaced above the grate and extending rearwardly from the opening 25. These arches are formed of refractory material capable of withstanding comparatively high temperatures in service, and in the preferred construction they are composed of separate refractory blocks, as shown in Fig. 3, these blocks being grooved on their .sides to t spaced parallel water tubes which support the blocks. The front arch 34 is supported by water tubes 36 which extend rearwardly from a transverse horizontal header 31 at the front of the arch, and the rear arch 35 is supported by water tubes 39 which extend forwardly from a transverse horizontalY header 40 at the rear of the arch. The headers 31V and 40 are supplied with water from the boiler drum I by means of one or more downcomer pipes M having branches V42 leading to the headers.

At the opening the water tubes'S and 39 are bent upwardly and extend along the corresponding bottom walls 23 and 24 in cooling relation with these walls, the upwardly extending posed f-ace of the rear wall IB and they may be connected directly with the boiler drum II, but in the case of a very high combustion chamber it will probably be dilllcult to obtain tubes of sufcient length. In such event'the upper ends of these tubes 33 will be connected to a transverse horizontal header 41 which vis connected to the drum I I by means of upright water wall tubes 48.

The water tubes 36 and 39 are arranged with A their centers spaced apart a distance of approximately twice the outside diameter of the tubes. With some fuels and operating conditions this may provide sufcient cooling for the sloping bottom walls 23 and 24. However, in order to make it possible to operate satisfactorily at high combustion rates with fuels having low ash-fusion temperatures, we preferably provide additional water tubes to form substantially completely water cooled metallic surfaces to direct the falling ashes into the opening 25. For this purpose we have provided a series of water tubes 5D with their opposite ends connected to the headers 43 and 41 in a staggered arrangement relative to the tubes 39. Along the rear wall It and the rear bottom wall 24 the tubes 50 are located in the same plane as the tubes 39, but adjacent the arch 35 the tubes 5U are bent outwardly with respect to the tubes 39 so that there will be no interference with the mounting of the refractory blocks of the arch on the tubes 39. A similar construction is utilized at the front of the furnace, where we have provided a series of water tubes 52 with their opposite ends connected to the headers 31 and 44 in a staggered arrangement with respect to the tubes 36. These tubes 52 are located in the same plane as the tubes 3E along the front bottom wall 23, but adjacent the arch 34 they are bent outwardly from the tubes 3S to avoid interference with the support of the refractory blocks of the arch.

The operation Yof the invention will now be apparent from the above disclosure. Pulverized fuel is discharged through the opening I8 by means of the burner I 9, and combustion takes place in the chamberv I4. Solid fuel, such as wood refuse, is delivered to the hopper 28 by the chute 75 portion of the fuel bed is radically different from that of the gases in the rear. Usually the gases at the front are somewhat deficient in air for combustion, whereas those at the rear may contain an excess of air. The arches 34 and 35 force all of these gases to enter the comparatively narrow throat 25, where a mixture takes place so .that all the combustible gases may be consumed efficiently and without undue quantities of air in excess of what is theoretically required. The hot gaseous products of combustion pass upwardly through the chamber I4 and into contact with the heating surfaces of the steam boiler thereabove in a well known manner. The ashes from the pulverized fuel separate from the flame by gravity and fall to the sloping bottom walls 23 and 24. Because of the cool metal surfaces afforded by the water tubes the ashes will not adhere to these walls but will slide down them and drop through the throat 25 to the grate 21. The grate will therefore serve as a means for conveying the pulverized fuel ash rearwardly and discharging the same. Either fuel may be burned alone if desired. In case pulverized fuel is being burned alone, the grate 21 may be operated continuously, or it may be operated intermittently whenever an appreciable quantity of ashes has accumulated thereon. Steam will of course be generated in the various water tubes and discharged upwardly into the drums I0 and II.

In the claims appended hereto we have for convenience used such expressions as transversely, longitudinally, forwardly, "rearwardly, etc., in order to set forth the claimed structure more clearly. It is to be understood, however, that these expressions are not to be considered as limitations except in so far as they define the relative positions of the various elements included in the claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. A furnace comprising walls enclosing a combustion chamber of sufficient size for the burning of pulverized fuel in suspension, means to supply pulverized fuel to the chamber for combustion in suspension therein, the chamber having two opposite bottom walls which are fully exposed to the radiant heat of the burning fuel and slope downwardly and inwardly toward a narrow central opening extending transversely of the combustion chamber, a longitudinally movable grate located beneath the opening, means to supply wood refuse to the grate for combustion thereon, arches of refractory material extending forwardly and rearwardly from the central opening to ensure ignition of fuel on the grate and to direct the gases arising from the fuel bed into the opening to mix said gases, and water circulating means supporting said arches and extending upwardly therefrom in cooling relation with said sloping bottom walls.

2. A furnace comprising walls enclosing a combustion chamber, means to supply fuel to the chamber for combustion in suspension therein, the chamber having two opposite bottom walls which slope downwardly and inwardly toward a narrow central opening extending transversely of the combustion chamber, a longitudinally movable grate located beneath the opening, means to supply fuel to the grate for combustion thereon, blocks of refractory material arranged to form arches which extend forwardly and rearwardly from the central opening to ensure ignition of the fuel on the grate and to direct the gases arising from the fuel bed into the opening to mix said gases, spaced water circulating tubes arranged to support the refractory blocks, the tubes having portions extending upwardly from the arches in cooling relation with said sloping bottom walls, and additional water circulating tubes located between the upwardly extending portions of the first mentioned tubes to provide additional water cooling for said sloping bottom Walls.

3. A furnace comprising walls enclosing a combustion chamber, means to supply fuel to the chamber for combustion in suspension therein, the chamber having two opposite bottom walls which slope downwardly and inwardly toward a narrow central opening extending transversely of the combustion chamber, a longitudinally movable grate located beneath the opening, means to supply fuel to the grate for combustion thereon, arches of refractory material extending forwardly and rearwardly from the central opening to ensure ignition of fuel on the grate and to direct the gases arising from the fuel bed into the opening to mix said gases, transverse headers adjacent the front portion of the front arch and the rear portion of the rear arch respectively, means to supply water to the headers, spaced water circulating tubes connected to the headers and arranged to support the arches, the tubes having portions extending upwardly from the arches in cooling relation with said sloping bottom walls, and additional water circulating tubes connected to the headers and extending above the arches and thence upwardly between the upwardly extending portions of the rst mentioned tubes to provide additional water cooling for said sloping bottom walls.

LOUIS E. GRIFFITH. OLLISON CRAIG. 

